The present invention relates to the art of refrigerant recovery and, more particularly, to an improved method and apparatus for recovering refrigerant from a refrigerating system having a high pressure liquid side and a low pressure vapor side and purging gas from the refrigerant during the recovery thereof.
The present invention finds particular utility in conjunction with refrigerant recovering apparatus operable in a liquid recovery mode and in a vapor recovery mode and which, when operating in the vapor recovery mode, is responsive to an unacceptably high pressure and thus temperature in the refrigerant recovery receptacle to disconnect the source of vapor being recovered from vapor reducing components of the apparatus and to circulate vapor in the recovery receptacle to the vapor reducing components for reduction to a liquid which is returned to the recovery receptacle, thus to reduce the pressure and temperature therein to acceptable levels. At the same time, as will become apparent hereinafter, the invention is applicable to refrigerant recovery methods and apparatus other than those including an arrangement for cooling the recovery receptacle during the vapor recovery operation.
A refrigerant recovery unit of the foregoing character is available from Ridge Tool Company of Elyria, Ohio under the latter's product designation Model RS-200 which is a portable unit for recovering a variety of refrigerants from air conditioning and other refrigeration systems having a high pressure liquid side and a low pressure vapor side from which refrigerant must be withdrawn in a recovery operation. This unit includes a casing enclosing the refrigerant recovery components including a compressor and condenser, flow lines and valving, and electrical circuitry which controls operation of the unit. The refrigerant recovery components provide liquid and vapor flow circuits having inlet ends selectively connectable through flexible hoses to the high pressure liquid and low pressure vapor sides of a refrigeration system from which refrigerant is to be recovered. The flow circuits have outlet ends connected to the refrigerant storage tank through a flexible hose. The refrigerant recovery components further include a vapor feed back circuit connectable to the storage tank through a flexible hose and by which vapor in the storage receptacle is adapted to be fed back to and through the vapor reducing components for return to the storage receptacle as a liquid. The electrical control circuit provides for the unit to be selectively operated in the liquid recovery mode and in the vapor recovery mode.
In the liquid recovery mode, liquid refrigerant from the refrigeration system is drawn directly into the storage receptacle, bypassing the vapor reducing components, and vapor in the storage receptacle is fed back and reduced in the foregoing manner and returned to the receptacle as a liquid. In the vapor mode, the vapor feedback circuit is closed and vapor is drawn from the refrigeration system and is reduced and pumped to the storage receptacle as a liquid. During vapor recovery, the pressure and thus the temperature in the storage receptacle can become undesirably high and, the pressure in the storage receptacle is monitored and, in response to an undesirably high pressure indicating an undesirably high temperature, the unit shifts to the liquid recovery mode whereby the vapor input from the refrigeration system to the vapor reducing components is blocked and the vapor feedback circuit is opened. This results in feed back of vapor from the receptacle to the vapor reducing components as described above, thus to reduce the pressure in and cool the storage receptacle. When the pressure is reduced sufficiently, the unit shifts back to the vapor recovery mode, whereby the feedback circuit is again closed and the input of vapor from the refrigeration system is recommenced so as to continue the vapor recovery operation. While it would be possible to discontinue operation of the unit during vapor recovery in response to an undesirably high temperature in the storage receptacle and then recommence the recovery operation when the temperature subsides sufficiently, the vapor feedback arrangement advantageously provides for minimizing the vapor recovery time by automatically providing a cooling function in conjunction with operation of the unit.
In connection with operating a refrigerant recovery unit of the foregoing character, it is of course necessary to purge air from the flexible hoses and from the liquid and vapor flow circuits prior to starting a recovery operation. Such purging is done manually and is time consuming. In this respect, the flexible hoses for connecting the high and low pressure sides of the refrigeration system with the recovery unit and for connecting the refrigerant storage receptacle with the unit include in-line valves to minimize the escape of refrigerant during start-up and shut-down of the equipment, and the storage receptacle has shut-off valves for the liquid and vapor line connections thereto. Moreover, as is well known, a refrigerating system from which refrigerant is to be recovered has service valves associated with each of the high pressure liquid and low pressure vapor sides of the system. Thus, there are 8 valves which have to be opened and closed and several hose connections which have to be loosened and tightened in connection with purging air from the equipment prior to initiating the refrigerant recovery operation. Moreover, when the unit is operating in the liquid recovery mode, or is shifted to the latter mode during vapor recovery as described above in response to an undesirably high pressure in the storage receptacle, the liquid flowing back to the receptacle from the vapor reducing components flows through a capillary expander. Non-condensable gases in the liquid, primarily air, cannot easily pass through the capillary tube and, thus, back up and accumulate in the condenser. This reduces the cooling capacity of the feedback flow circuit and thus increases the time required to lower the pressure in the storage receptacle to the level at which the unit shifts back to the vapor recovery mode. This in turn increases the overall time required to complete the vapor recovery operation.